To find the inverse of the function \( C(x) = x + 4 \), we need to determine a function \( C^{-1}(x) \) such that when applied to the output of \( C(x) \), it returns the original input \( x \). This involves solving the equation \( y = x + 4 \) for \( x \), which gives us \( x = y - 4 \). Therefore, the inverse function is \( C^{-1}(x) = x - 4 \).
Step 1: Define the Inverse Function
To find the inverse of the function \( C(x) = x + 4 \), we start by setting \( y = C(x) \). This gives us the equation:
\[
y = x + 4
\]
To isolate \( x \), we rearrange the equation:
\[
x = y - 4
\]
Thus, the inverse function is defined as:
\[
C^{-1}(x) = x - 4
\]
Step 2: Calculate the Original Number
Using the inverse function, we can find the original number corresponding to an encoded number. For example, if we take \( \text{encoded\_number} = 11 \):
\[
\text{original\_number} = C^{-1}(11) = 11 - 4 = 7
\]
Step 3: Interpret the Result
The original number \( 7 \) corresponds to the letter \( G \) in the alphabet, as per the given encoding scheme.
Final Answer
The original number corresponding to the encoded number \( 11 \) is \( \boxed{7} \).